Storms and Flooding and Climate Change

Riverine flooding is the most common natural disaster in New Hampshire. Over the past ten years, the state has experienced four severe flooding events, costing the state millions of dollars in damage from blown out culverts, flooded roads, and severe erosion on stream banks. The resulting sediment and debris also polluted streams, rivers, lakes, and ponds, and changed aquatic habitats.

Scientists predict that annual average precipitation will increase 14-20% and that the number of extreme storms will increase threefold, resulting in a greater risk of flooding. Storms will be less frequent but more severe in intensity, and there will be longer dry periods between storms.

Floodplain habitats may experience more flooding and will also be affected by summer drought. Examples of storms that have affected New Hampshire include the Mother’s Day storm of 2006, April of 2007, Hurricane Irene in 2011, and Hurricane Sandy in 2012. These storms caused blown out culverts, flooded roads, and severe erosion. The resulting sediment and debris polluted streams, rivers, lakes, and ponds and changed habitat structure and function. The long-term result may be altered species composition, including more invasive species.

How Extreme Storms and Flooding Affect Wildlife

According to the NH Wildlife Action Plan, storms and flooding are the natural disasters that affect the greatest number of species and habitats. Extreme storms can disrupt bird migrations and make breeding and nesting sites inhospitable, forcing birds into marginal habitats, which can reduce their chance of survival. Flooding alters the flow of streams and rivers and increases the amount of pollutants and sediments that wash into them. Species can be swept downstream or killed. Sediment can cover spawning habitat for fish, smother aquatic wildlife, kill eelgrass beds, and clog the feeding mechanisms of mussels.

Storm water also floods nesting sites along the banks of rivers and ponds and in the marshes downstream, affecting species such as loons and wood turtles. One of the major impacts is the destruction of stream crossings (culverts) in watersheds all over the state. When a functioning culvert collapses, the connectivity throughout the watershed is destroyed, making it impossible for aquatic species such as brook trout to migrate to their spawning grounds or to seek refuge in cooler areas of the stream.

Coastal ecosystems are particularly susceptible to storms that disrupt dunes, salt marshes, eelgrass beds, and water quality. This brings additional stress to species living in these habitats, including fish, shellfish, nesting plovers, saltmarsh birds, and seabirds. In estuarine systems, the influx of freshwater and stormwater runoff may alter and carry pollutants into the water, increase salinity, and change water temperatures, leading to shifts in the distribution of species and increased stress and mortality.

What NH Fish and Game Is Doing in Response to Extreme Storms and Flooding

The Fish and Game Department is developing partnerships with other federal and state agencies, local communities, and landowners to inventory and replace stream crossings to improve passage for aquatic species to travel throughout a watershed. Fish and Game biologists incorporate increased precipitation estimates into models that inform estuarine habitat restoration efforts and track changes in temperature and salinity through water quality monitoring.

Techniques and infrastructure that reduce storm water impacts, including erosion, and mimic the natural flood protection functions of dunes and saltmarshes are encouraged and used by Fish and Game when possible.

Extreme Storms and Flooding and People

More frequent and severe storm events with associated flooding can cause serious economic impacts due to clean up, repair, and lost productivity. All of us benefit from letting floodplains accomplish their natural function of mitigating excess storm water. Effective stream crossings maintain safe public roads and also prevent flooding and erosion of stream banks.

Taking Action

• Participate in a stream crossing survey in your town and pursue grant funding to help fix stream crossings.
• Replace asphalt with naturally draining surfaces so rainwater is absorbed into the ground.
• Promote zoning ordinances to protect floodplain habitat.
• Educate yourself and share your understanding with friends and family about how climate change affects wildlife and habitats. 
• Start planning now for good ecological health and get involved in your local community by addressing potential climate change issues in your town or region. 
• Support and volunteer for environmental and conservation organizations that address climate change impacts to wildlife and habitats.
• Become a citizen scientist and help collect data on plants, wildlife, water, and weather.
• Plant native vegetation along water bodies to reduce erosion.